Device for metering refrigerant flow to an evaporator and systems incorporating same

ABSTRACT

Metering devices suitable for incorporation into vapor-compression refrigeration systems are disclosed, having adjustable features that allow them to regulate the pressure drop across them. These devices include a screw with flights positioned to define a path for the liquid refrigerant to flow through, causing frictional pressure losses. Refrigerant systems incorporating these metering devices are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/476,676 filed Jun. 6, 2003.

FIELD OF THE INVENTION

The present invention relates to valves and metering devices inrefrigeration loops and refrigerant based test systems, useful forexample in the automotive, HVAC, home appliance and industrialrefrigeration fields. More particularly the present invention relates tosuch devices suitable for the control of pressure drop within arefrigeration loop, and systems incorporating such devices.

BACKGROUND OF THE INVENTION

Conventional vapor and compression refrigeration loops incorporate acondensor and an evaporator, in fluid connection with a compressor and ametering device. The metering device is positioned between the condenserand the evaporator to lower the pressure of the liquid before it isevaporated. Traditionally, this is accomplished using either a capillarytube or a thermostatic expansion valve.

In operation, a capillary tube uses a channel having a specific lengthand diameter to create frictional losses, resulting in pressure drop ofthe liquid as it traverses through the channel. This equipment has thedisadvantage that it is not adjustable to suit a variety of desiredpressure drops, inasmuch as both the length and the diameter ofcapillary tube used in the refrigeration system is constant or fixed.Given this limitation, the amount of superheated fluid that leaves theevaporator is also not adjustable, so that liquid could reach thecompressor should the operating conditions change.

A thermostatic expansion valve overcomes this problem, but such valvesare typically bulky and expensive to manufacture.

It is an object of the present invention to provide a metering valvesuitable for use in refrigeration systems, which allows for adjustmentsin desired pressure drop across the device. A further object of thepresent invention is to provide such a metering valve which canincorporate a variety of fluid flow configurations therealong. A featureof the present invention is that it can be retrofitted into existingrefrigeration systems including those used in HVAC and automotiveapplications. It is an advantage of the present invention to provide ametering valve with a minimal number of parts which promotes longservice life. These and other objects, features and advantages of thepresent invention will become better understood upon having reference tothe description of the invention herein.

SUMMARY OF THE INVENTION

There is disclosed and claimed herein a device suitable for metering theflow of fluid therealong, comprising:

-   -   (a) a casing defining an inlet port, a side port and an end        port; and    -   (b) a screw positioned within said inlet port and sufficient to        block the flow of fluid therethrough, said screw comprising a        member and flights positioned along all or a portion of the        length of said member,    -   such that fluid entering said side port or said end port flows        along a pathway defined by said member and said flights of said        screw sufficient to achieve a desired frictional pressure loss        and thereafter exits said end port or said side port,        respectively.

The invention will become better understood upon having reference to thedrawings herein.

IN THE DRAWINGS

FIG. 1 is a schematic diagram of a conventional vapor-compressionrefrigeration cycle;

FIG. 2 is a cross sectional side view of one embodiment of the deviceaccording to the invention with the valve sealing to the threadstherein; and

FIG. 3 is a cross sectional side view of another embodiment of thedevice according to the invention with the valve sealing to the shafttherein.

DETAILED DESCRIPTION OF THE INVENTION

Having reference to FIG. 1 herein, there is shown generally at 10 aschematic of a typical refrigeration cycle. Those having skill in thisfield will readily appreciate the thermodynamics associated with thisdiagram. In general, an evaporator 12 and a condenser 14 are in fluidconnection with each other. The compressor 16 is positioned to receivefluid from the evaporator 12 and feeds into the condenser 14. A meteringdevice 18 is positioned to receive fluid from the condenser 14 and feedsinto the evaporator 12. Passages 20 (as piping, tubing and the like)connect each of the elements above in the aforementioned sequence.

Having reference to FIG. 2 herein, there is shown generally at 22 oneembodiment of the metering device 18 of the invention herein. Thismetering device 18 includes a casing 24 (typically tubular) with aninlet port 26 and a screw 28 positioned around the member 40. The liquidrefrigerant enters through either the side port 30 or the end port 32and is forced around the flights 34 of the screw 28 (and outside themember 40) until it exits at the end port 32 or the side port 30respectively. These flights 34 can be any shape or size, and areconfigured to develop a desired path length for the liquid refrigerantto flow therealong. The pressure drop is achieved by the liquidrefrigerant traveling the path defined by the screw 28 and the member40, which causes frictional pressure losses. The screw 28 is fittedthrough a sealed hole 36 in the inlet port 26 so that it can beretracted or inserted to adjust the length of the path that the fluidmust travel before it reaches the exit (either side port 30 or end port32).

Having reference to FIG. 3 herein, there is shown generally at 38another embodiment of the metering device 18 of the invention herein.The design depicted in FIG. 3 is identical to that in FIG. 2 exceptinstead of forming the sealed hole 36 with the flights 34 of the screw28, an unthreaded member 40 is positioned at the end of the screw 28closest to the sealed hole 36 and the seal is thereby made with thisunthreaded member 40. Both configurations allow the pressure drop to beadjusted to the proper amount to give desired superheating.

Various attributes of the invention as described above can bemanufactured according to conventional techniques, all as is readilyunderstood by those of relevant skill in the art. For example, thesealed hole 36 may be sealed by fitting in place an elastomeric compoundsuitable for withstanding the motion through the sealed hole 36 andresistant to degradation by the elements and the refrigerants. Themember 40 and the flights 34 are likewise constructed from materialsthat function in place for extended periods of time and without failure,and such that they are mechanically sound and resistant to chemicalattack. Metals such as aluminum are attractive for this purpose. Finallythe casing 24 can be made of a variety of materials including a widearray of metals and plastics, such that they meet design specificationsfor overall size and shape and function to retain the fluidstherewithin. Copper and brass can be selected as useful materials in thedesign of a durable assembly according to the invention.

It is readily understood and appreciated that those having skill in theart to which this invention pertains can make any number of variationsand modifications to the invention as set forth and described herein.Such enhancements are contemplated as within the spirit and scope of theinvention.

1. A device suitable for metering the flow of fluid therealong,comprising: (c) a casing defining an inlet port, a side port and an endport; and (d) a screw positioned within said inlet port and sufficientto block the flow of fluid therethrough, said screw comprising a memberand flights positioned along all or a portion of the length of saidmember, such that fluid entering said side port or said end port flowsalong a pathway defined by said member and said flights of said screwsufficient to achieve a desired frictional pressure loss and thereafterexits said end port or said side port, respectively.
 2. The meteringdevice of claim 1 wherein said flights of said screw extend along saidmember and contact said inlet port.
 3. The metering device of claim 1wherein said flights of said screw extend along said member but do notcontact said inlet port.
 4. A vapor-compression refrigeration cyclesystem incorporating the metering device of claim 1, wherein saidmetering device receives fluid from a condenser and directs fluid to anevaporator.